Piston



' June 24, 1930.

D. E. slvl'rrHl PISTON Filed July 9, 1927 @noauto/a Patented .lane 24,w3@

VPAirNr orion :Davis E. sMITH, or nnrnoir, MicnIcfANY ris/ronApplication filed. July 9, v1927. Y Serial No. 204,531.

The present invention pertains to e. novel piston of the trunk typeadapted `for use particularly in internal combustion engines where ahigh temperature is established in the cylinders.

The principal object ofthe invention is to provide a piston ot thischaracter constructed of aluminum alloy or other materi-al having a highco-eiicient of expansion and wherein` there is provided a means Yforreducing the expansion of such material.

The expansion et aluminum alloy pistons used in common practice is muchgreater than the expansion of the cylinder and the pistons` areconsequently itted with sufli cient clearance to accommodate the pistonexpansion under the highest temperature in the cylinder. This clearanceis, however, detrimental before the cylinder reaches its maximumtemperature which is necessary in order that the piston may properly littheJ cylinder. Consequently, while the cylinderis cool, the operation isimpeded by piston slap, disagreeable noise, excessive wear on the pistonand cylinderwalls, and leakage of oil past the piston rings.

The present invention overcomes these difficulties by the provision ofan insert of low thermal expansion material in the wall of the pistonbody so that the expansion of the latter is limited.

The invention is Jfully disclosed by Way of example in the followingdescription and in the accompanying drawings, in which Figure l is alongitudinal section of the device, partly in elevation;

F 2 is a longitudinal section on the line II-II of Fig. Vl; g y

Fig. 3 is an elevation of the tubular insert, and f Fig. l is asectional view of a modified construction.

eierence throughout. e

The piston illustrated in the several tigures includes a head1 and askirt 2 between which is formed a transverse Vbearing 3. The bearing isjoined to the head by means VVot the head and skirt, and with thisobject to these views will nowV beV made by use of likeV characterswhich arey employed to designate corresponding partsv -oi' an aluminumalloy piston without the of ribs 4 at the ends of the bearing. Theseparts are made oit' aluminum, and in ordinary practice must beconsiderably smaller than the cylinder at low temperaturev in order thattheir excessive expansion at high 55 temperature may be accommodated inthe. cylinder. This principle of construction is the cause of numerousdefects already described. In order to avoid such detrimental clearancebetween the cylinder wall and pisa() ton at low temperature, I form thepiston of such size as to lit the cylinder reasonably well even at lowtemperature, and thenk provide the piston with an inner member of a low(zo-efficient of expansion in order to prevent excessive expansion ofthe piston at 1 the higher cylinder temperatures.

This insert consists of a tube Geformed" preferably of nickel steel. Itis embedded in the walls of the head and skirt as indicated by numerals7 and 8 respectively, and extends circumferentially of these parts inorder to retain the same at allpoints. The insert may be positionedduring the casting in View it is formedV with pertorations 9 whichafford betterl adhesion of the alloy thereto. Also, the insert isJformed with larger openings l0 which aline with the ends i of thebearing 3. In case the skirt 2 has a diameter greater than theflength ofthev bearing 3, the insert is flared as at 11 from the bearing to theskirt.

It is desirable to avoid excessive expansion particularly in the'skirt,and the con-` struction m-ay accordingly be simplied as illustrated inFigure 4. In this case the insert is merely a ring or band 12 embeddedin theskirtl without extending upwardly into the head of the piston. Y,'i .90

As already stated, the piston is dimensioned to run fairly well in thecylinder even' at low temperatures. The natural highexpansion of thealuminum alloy at higher temperatures is .restrained by thev steel insert V6 which has a comparatively low co-ehicient of expansion. Theresult of this construction is a device having the advantage attendantdifficulties 0f clearance and high expansion of the material.

Although a specific embodiment of the invention has been illustrated,and described, it will be understood that various altera-tions in thedetails of Construction may be made 1without departing from the scope ofthe invention as indicated by the appended claim.

What I claim is In a piston of high thermal expansion material having ahead and a separate skirt,

a separa-te tubular member of low expansion v material insertedCircumferentially in the Wall of said head and skirt and forming aConnecting means therebetween.

In testimony whereof I affix my signature.

DAVIS E. SMITH.

